Hox Gene - Genes Regulated By Hox Proteins

Genes Regulated By Hox Proteins

Hox genes act at many levels within developmental gene hierarchies: at the "executive" level they regulate genes that in turn regulate large networks of other genes (like the gene pathway that forms an appendage). They also directly regulate what are called realisator genes or effector genes that act at the bottom of such hierarchies to ultimately form the tissues, structures, and organs of each segment. Segmentation involves such processes as morphogenesis (differentiation of precursor cells into their terminal specialized cells), the tight association of groups of cells with similar fates, the sculpting of structures and segment boundaries via programmed cell death, and the movement of cells from where they are first born to where they will ultimately function, so it is not surprising that the target genes of Hox genes promote cell division, cell adhesion, apoptosis, and cell migration.

Examples of targets
Organism Target gene Normal function of target gene Regulated by
Drosophila distal-less activates gene pathway for limb formation ULTRABITHORAX

(represses distal-less)

distal-less activates gene pathway for limb formation ABDOMINAL-A

(represses distal-less)

decapentaplegic triggers cell shape changes in the gut that are

required for normal visceral morphology

ULTRABITHORAX

(activates decapentaplegic)

reaper Apoptosis: localized cell death creates the segmental

boundary between the maxilla and mandible of the head

DEFORMED

(activates reaper)

dapentaplegic prevents the above cell changes in more posterior

positions

ABDOMINAL-B

(repress decapentaplegic)

Mouse EphA7 Cell adhesion: causes tight association of cells in

distal limb that will form digit, carpal and tarsal bones

HOX-A13

(activates EphA7)

Cdkn1a Cell cycle: differentiation of myelomonocyte cells into

monocytes (white blood cells), with cell cycle arrest

Hox-A10

(activates Cdkn1a)

Read more about this topic:  Hox Gene

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